linux-kernel - Re: [PATCH] enhanced reimplemention of the kfifo API

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Date:	Thu, 4 Feb 2010 09:58:18 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Stefani Seibold <stefani@...bold.net>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	Andi Kleen <andi@...stfloor.org>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Theodore Tso <tytso@....edu>,
	"Ira W. Snyder" <iws@...o.caltech.edu>
Subject: Re: [PATCH] enhanced reimplemention of the kfifo API

On Thu, 04 Feb 2010 17:52:40 +0100
Stefani Seibold <stefani@...bold.net> wrote:

> ...
> > > > > +#define	kfifo_out_locked(fifo, buf, n, lock) \
> > > > > +__kfifo_check( \
> > > > > +({ \
> > > > > +	unsigned long __flags; \
> > > > > +	unsigned int __ret; \
> > > > > +	spin_lock_irqsave(lock, __flags); \
> > > > > +	__ret = kfifo_out(fifo, buf, n); \
> > > > > +	spin_unlock_irqrestore(lock, __flags); \
> > > > > +	__ret; \
> > > > > +}) \
> > > > > +)
> > > > 
> > > > This is poorly named.  Generally "foo_locked" is to be called when the
> > > > caller has already taken the lock.  This identifier inverts that
> > > > convention.
> > > > 
> > > 
> > > This is the same name as the current kfifo API. Renaming it would break
> > > a lot of drivers. But if there is no complain and you insist i will
> > > rename it and fix the current users.
> > 
> > argh, we goofed.
> > 
> > yeah, it'd be nice to fix it sometime, please.  Not urgent.
> > 
> > A good way to fix it would be to add a new function with a new name
> > then migrate all callers over to that name then when it's done, remove
> > the old name.
> > 
> 
> I will do this in the next release. Would be kfifo_out_spinlocked() and
> kfifo_in_spinlocked() for the new names okay?

Good enough.  It's a bit sad to needlessly expose the type of lock in
the identifier but not the end of the world.

> 
> One offer to solve the egg and chicken problem: Let us include the
> functions kfifo_to_user(), kfifo_from_user(),  kfifo_esize(),
> kfifo_recsize() and the dynamic record handling. If there will be no
> users in at least 9 months we remove it from the API. We talk here about
> 400 bytes of code.
> 
> In the mean time me and other developer will have a change to modify the
> existing driver to the new API and/or post drivers or core kernel code
> which is using this functionality. 
> 

Sounds OK to me.
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